Editing Resistor (section)

===Wire wound===
[[File:KTSU resistors.jpg|thumb|right|High-power wire wound resistors used for [[dynamic braking]] on an electric railway car. Such resistors may dissipate many kilowatts for an extended length of time.]]
[[File:Types of winding by Zureks.png|thumb|Types of windings in wire resistors: {{ordered list |common |[[bifilar winding|bifilar]] |common on a thin former |[[Ayrton–Perry winding|Ayrton–Perry]]}}]]

Wirewound resistors are commonly made by winding a metal wire, usually [[nichrome]], around a ceramic, plastic, or fiberglass core. The ends of the wire are soldered or welded to two caps or rings, attached to the ends of the core. The assembly is protected with a layer of paint, molded plastic, or an [[Vitreous enamel|enamel]] coating baked at high temperature. These resistors are designed to withstand unusually high temperatures of up to 450&nbsp;°C.<ref name=Vishay08/> Wire leads in low power wirewound resistors are usually between 0.6 and 0.8&nbsp;mm in diameter and tinned for ease of soldering. For higher power wirewound resistors, either a ceramic outer case or an aluminum outer case on top of an insulating layer is used. If the outer case is ceramic, such resistors are sometimes described as "cement" resistors, though they do not actually contain any traditional [[Portland cement|cement]]. The aluminum-cased types are designed to be attached to a heat sink to dissipate the heat; the rated power is dependent on being used with a suitable heat sink, e.g., a 50&nbsp;W power rated resistor overheats at a fraction of the power dissipation if not used with a heat sink. Large wirewound resistors may be rated for 1,000 watts or more.

Because wirewound resistors are [[Electromagnetic coil|coils]] they have more undesirable [[Electromagnetic induction|inductance]] than other types of resistor. However, winding the wire in sections with alternately reversed direction can minimize inductance. Other techniques employ [[bifilar winding]], or a flat thin former (to reduce cross-section area of the coil). For the most demanding circuits, resistors with [[Ayrton–Perry winding]] are used.

Applications of wirewound resistors are similar to those of composition resistors with the exception of high frequency applications. The high frequency response of wirewound resistors is substantially worse than that of a composition resistor.<ref name=Vishay08/>